The invention relates to improvements in apparatus for transmitting torque between a rotary input element and a rotary output element. More particularly, the invention relates to improvements in torque transmitting apparatus of the type embodying one or more dampers which prevent the transmission of oscillations and/or other undesirable changes of torque which is being transmitted between a rotary input element and a rotary output element. Still more particularly, the invention relates to improvements in dampers which are or which can be utilized in the power trains between the prime movers (such as combustion engines) and variable-speed transmissions and/or other driven units of motor vehicles.
It is known to utilize in the power train of a motor vehicle a damper which includes at least one set of arcuate energy storing elements (e.g., in the form of coil springs), a rotary input member which normally receives torque from the rotary output element (e.g., a crankshaft or a camshaft) of an engine, and a rotary output member which can transmit torque to a variable-speed transmission. The energy storing elements serve to yieldably oppose angular movements of the input and output members relative to each other. The input member of the damper can constitute a first or primary flywheel which can be attached to the rotary output element of an engine, and the output member of the damper can include or can constitute a second or secondary flywheel which can drive the input shaft of a variable-speed transmission by way of an engageable and disengageable friction clutch. Reference may be had, for example, to published German patent applications Nos. 39 09 892, 41 17 571 and 41 17 579 as well as to the corresponding patent applications and/or patents applied for and granted in countries other than Federal Republic Germany.
Torque transmitting apparatus embodying dampers of the character disclosed in the aforementioned published German patent applications have met with considerable success. However, the operation of dampers presently utilized in such torque transmitting apparatus is not entirely satisfactory when the apparatus is installed in certain types of motor vehicles and under certain circumstances of the use of such vehicles. For example, certain types of combustion engines, power trains between the engines and the wheels and/or chassis of the respective vehicles cause the generation of undesirable noise, such as humming, when the RPM of the output element of the engine is within a certain range. Such noise is more likely to develop when the vehicle is coasting, i.e., when the wheels transmit torque to the power train which, in turn, transmits torque to the output element of the engine. The reason for the generation of such noise, particularly when the vehicle is coasting, is believed to be that the heretofore known dampers are incapable of preventing the transmission of oscillatory and other stray movements between the input and output members of the dampers.